Given the rise in gun related violence in urban areas and the increasing involvement of U.S. troops in worldwide peace keeping operations there now exists a need for a security system having capabilities to quickly detect, locate and classify the source of gunfire with a high degree of reliability and accuracy. The system should also provide rapid notification to local law enforcement authorities, rescue teams or military personnel, as the case may be, while aiding in locating gunshot victims and apprehension of perpetrators. Such a system must also be able to withstand the harsh environment of an urban setting or war zone, be inconspicuous, and require a minimum of maintenance while allowing for the easy placement and removal. The necessity for such an invention is premised on a long felt need for rapid response by police, peace keeping troops and rescue teams in order to significantly increase the apprehension rate of perpetrators and the survival rate of gunshot victims.
One known device, the G.R.A.I.D..TM. by 3-I, Inc. is a gunshot detector for use in silent alarm devices. In one application, when a firearm is discharged, a detector activates hidden cameras and notifies either the police or an alarm company. In another application of the G.R.A.I.D..TM. device, it is installed in the front grill of a police car whereby it can detect a gunshot near the vicinity of the police car by separating the profile of gunshot from that of other common noises. In a situation where a police officer is wounded by gunfire, or discharges his weapon, the G.R.A.I.D..TM. device commences a sequence to summon aid by opening the police transmitter, generating a series of codes distinct to each car which is transmitted over police radio for two seconds and is repeated at one minute intervals until the system is reset. The transmission is received at the dispatch desk by decoding receiver where the transmission is converted into the number of the sending vehicle. The receiver sounds an alarm and displays the number of the sending vehicle with time and day. The receiver is reset and the vehicle contacted. If no contact is made with the transmitting vehicle the code will be repeated and the receiver will continue to trip once each minute. After five minutes, the vehicle's horn will sound for five seconds each minute to assist responding officers in locating the vehicle.
U.S. Pat. No. 3,341,810 to Wallen et al. entitled "Gunshot Detector System", teaches a system designed to function in an extreme ambient noise environment for detecting and distinguishing gunshot muzzle blasts and acoustic pressure waves of gun-launched projectiles passing in proximity to a target on which the system is mounted.
Wallen, et al. teaches a system wherein a plurality of detecting networks are placed on a high level ambient noise platform, such as a helicopter. Utilizing pressure waves generated from an object passing at high speed, in this case a bullet, the plurality of detecting networks is able to determine the range and distance of the source by calculating the intensity of the pressure wave, with muzzle indications provided only if the distance between the detecting site and the originating point of the report exceeds a predetermined amount. The Wallen et al. device determines and processes two disparate frequencies within the ultra-sonic range to reduce the effect of ambient noise. The location of the muzzle blast is provided only if the distance between the detecting site and the originating point of the report exceeds a predetermined amount.
Unfortunately, prior devices as discussed above have not proven especially effective in discriminating gunshot events from other types of similar acoustic events such as exploding fireworks, slamming car doors, hammer hits, and motor vehicle backfires. In contrast to the prior art, the present invention takes advantage of a new discovery that rear acoustic detection from a gunshot event provides discrimination information which may be used to improve repeatable discrimination of a gunshot event from other types of high acoustic events such as those listed above. Furthermore, systems of the prior art, are extremely limited in range and may not effectively work at ranges over 100 feet or less.